The use of aromatic amines as stabilizers for lubricant compositions is well-known in the art. U.S. Pat. Nos. 3,509,214 and 3,573,206 typify the state of the art for such products.
It is well-known that many organic liquids and solids used in industrial applications, such as oils and greases, power transmission fluids, resin and polymer coatings, insulations, structural products and the like, may deteriorate when subjected to oxidation. Since these substances are very often used at high temperatures, the rate of oxidative breakdown can be very rapid. This problem is particularly important in the operation of modern day automotive and aircraft engines. The breakdown of the lubricating oil, either natural or synthetic, is frequently accompanied by the formation of corrosive acids, sludge and other breakdown products. These resulting products can harm the metal surfaces of the engine and interfere with the efficient operation of the lubricants.
U.S. Pat. Nos. 3,509,214 and 3,573,206 disclose that the stability of the organic compounds used in such lubricants which are normally susceptible to oxidative deterioration could be unexpectedly improved by the addition thereto of an N-arylnaphthylamine containing lower oligomer obtained by subjecting said N-arylnaphthylamine or mixture of said N-arylnaphthylamine with a diphenylamine or a second N-arylnaphthylamine to either thermal or chemical oxidation or both.
A number of N-alkyl substituted 2,3-dihydroperimidine compounds are known in the prior art as seen below:
J. Org. Chem. 51, 370 (1986) describes 2-chloro-1,3-dimethyl-1H-perimidine;
Zh. Org. Khim. 17, 1005 (1981); Chem. Abst. 95, 187185r describes the general synthetic methods used to prepare 1-alkyl-2,3-dihydroperimidines;
Zh. Org. Khim. 20, 1567 (1984); Chem. Abst. 102, 6382x (1985) describes 2,2'-bis(2,3-dihydroperimidines).
U.S. Pat. No. 4,389,321 describes selected 2,3-dihydroperimidines which are useful as antioxidants for lubricant compositions. Although these compounds are peripherally related to some of the instant compounds, none of the compounds of this reference are substituted on the N-atom with an alkenyl or sulfur-containing moiety.
U.S. Pat. No. 3,185,538 describes various substituted perimidinium halide methine dye salts useful for coloring polyacrylonitrile. U.S. Pat. No. 4,224,071 discloses nitro-substituted monoazo dihydroperimidines which are useful as black dyes for ballpoint pen inks. U.S. Pat. Nos. 4,224,326 and 4,294,964 describe selected 2-aryl-1H-perimidines which are useful as immunosuppresive agents. U.S. Pat. No. 4,565,424 discloses some dichroic poly(arylazo) dyestuffs having inter alia some dihydroperimidine end groups. None of these references describe compounds which are substituted on the N-atom with an alkenyl or sulfur-containing moiety.
The instant invention pertains to N-alkenylated, preferably N-allylated or N-methallylated, and N-methylene-thio substituted 2,3-dihydroperimidines which have been found to have superior antioxidant properties in lubricant compositions.